The steadystate Heat Loss calculation includes results on Preheat Periods and Plant Ratios. This article details where the specific hours shown arise from, and why they may not appear on your results.
Preheat Periods and Plant Ratio results will always be enabled in results by default, if it is applicable to the rooms that are being calculated.
The pre-heat times displayed are based on the occupancy schedules selected for the room(s) in question - eg if your rooms are set to be occupied for 24 hours a day then there will be no possibility to preheat prior to occupancy.
Taking one room for example: